You must remember you have a engine block which houses your pistons on your motorcycle. It is the pistons that actually drive the engine crank that transfers energy to your transmission. The "heads" as you put it sit on top of the block. The heads consist of at a minimum of 2 ports per piston. One for the fuel air mixture and one for the exhaust. Timining in an engine is set such that on every other stroke of the piston the engine is exhausting or combusting. When the piston 1 is beginnning at the top of the stroke a port(or valve) is opened(this is in the head) which allows the fuel air mixture into the piston chamber. When timing is correct the spark from the spark plug ignites the mixture which drives the piston down. The port is then closed. When the piston comes up again the the other port opens which allows the combusted materials(exhaust) to exit the chamber. The idea behind porting and polishing had to do with having the area in the head that gases enter and exit the chamber are clean and smooth. This Gentleman and Lady friend are making sure they are heading for a safe and enjoyable trip.